I was just reviewing the verses in the book of Revelation about the prophets, martyrs and saints being killed in Rev. 17:6 & 18:24 by the woman Mystery Babylon, but I previously missed seeing Rev. 16:6 about the prophets and saints also being killed by the men taking the mark of the beast and worshipping his image.

Rev. 16:6, "For they have shed the blood of saints and prophets, and thou hast given them blood to drink; for they are worthy."

The word "they" in the above verse is referring to the people who took the mark of the beast and worshipped the beast's image and not the woman Mystery Babylon in Rev. 18:24 in which was in her found the blood of the prophets, and of the saints and all that were slain on earth.

Please reread Rev. 16:1-6 about the first 3 vial judgments poured out by the angels:

"And I heard a great voice out of the temple saying to the seven angels, Go your ways, and pour out the vials of the wrath of God upon the earth.  And the first went, and poured out his vial upon the earth; and there fell a noisome and grievous sore upon the men which had the mark of the beast, and upon them which worshipped his image. And the second angel poured out his vial upon the sea; and it became as the blood of a dead man: And the third angel poured out his vial upon the rivers and fountains of waters; and they became blood. and every living soul died in the sea. And I heard the angel of the waters say, Thou art righteous, O Lord, which art, and wast, and shalt be, because thou hast judged thus. For they have shed the blood of saints and prophets, and thou hast given them blood to drink; for they are worthy."

My point being that no where in past history has anyone taken the mark of the beast nor worshipped the beast's image until the great tribulation period.   During the great tribulation period both the woman Mystery Babylon and those taking the mark of the beast and worshipping his image are responsible for killing the prophets , the martyrs, the saints and all who are killed on Earth during the great tribulation period of 1,260 days.